This invention relates generally to radio frequency networks in which a plurality of devices communicate with one another using radio frequency signals.
A piconet is radio frequency network in which a plurality of devices communicate over an established protocol. One such an established protocol is the Bluetooth specification. See for example, revision b of the Bluetooth specification dated Jul. 2, 1998. The Bluetooth technology is a short range, cable replacement radio technology using the 2.4 GHz Industrial Scientific and Medical (ISM) band. Generally, the range of the existing Bluetooth devices is about 10 meters.
In a Bluetooth network, all units are peer units using essentially identical radios except for a unique 48 bit address. At the start of a connection, an initializing unit is temporarily assigned as a master. That assignment is valid only during that connection. The master initiates the connection and controls the traffic of up to seven slave units.
Units then may be dynamically connected to the piconet at any time. A connection is made either by a page message issued by a master, if an address is already known, or by an inquiry message followed by a subsequent page message if the address is unknown. In the initial page mode, the master sends a train of sixteen identical page messages on sixteen different hop frequencies defined for the slave unit being paged. The train covers half the sequence of frequencies in which the slave can wake-up and is repeated 128 times. If no response is received, the master transmits a train of sixteen identical page messages on the remaining sixteen hop frequencies in the wake-up sequence. The maximum delay before the master reaches the slave may be 2.5 seconds.
Inquiry messages are very similar to the page message but may require one additional train to collect all the responses. If no data needs to be transmitted, the piconet units may be put on hold where only an internal timer is running. When the units go out of the hold state, data transfer can be restarted instantaneously. The units may thereby remain connected, without data transfer, in a low power state. Data may be exchanged over synchronous connection oriented (SCO) links or asynchronous connectionless (ACL) links.
A personal area network is a network that may be established using Bluetooth technology, for example, between a master and a plurality of proximate slave devices. A personal area network generally involves a piconet wherein a plurality of devices commonly owned by one person are able to communicate with one another without using cables.
Thus, personal area networking is generally limited to the connection between proximate devices. In the case of Bluetooth-style piconet, that means that all of the devices in the piconet are within ten meters of one another.
However, in a variety of different circumstances any one user may have devices that the user wishes to communicate with that are spaced much farther than ten meters apart. For example, a user may have a home computer and a computer at work that are more than ten meters apart. Because of the range limitations of conventional cable replacement radio frequency protocols, communications between such remote devices in different piconets is currently not possible. Each of the piconets, set-up on an ad hoc basis, is effectively isolated in a local ten meter region.
Thus, there is a need for a way to enable piconets to communicate with one another at distances greater than the range of the particular radio frequency protocol utilized to establish the piconet.